PHL Bass Midrange 8 ohm vs 16 ohm - same SPL: Why ? - diyAudio
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Old 27th March 2010, 12:28 AM   #1
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Default PHL Bass Midrange 8 ohm vs 16 ohm - same SPL: Why ?

In the box from the attached picture, that I use for demonstation by customers, which want to diy their own loudspeaker, I use a model from the french brand PHL, that I can order in 8 ohms (model 1220) and 16 ohms (model 1230) - go to Welcome on PHL audio web site
or
http://www.phlaudio.com/datasheets/17_pdf/1220_1230.pdf
By compare the value for sound presure level (SPL) at both impedances I observe a curios thing:

The value at 16 ohms is the same (almost - only 0,3db less) than by the 8 ohm version, based on the output voltage and not on the output power as mentioned in the pdf datasheet.

Which reason could be therefore present?
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Old 27th March 2010, 01:30 AM   #2
wahab is offline wahab  Algeria
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Do not know about this one, but PHL makes very good speakers,
I had some in a Zeck PA system.
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Old 27th March 2010, 03:06 AM   #3
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Default Just a difinition...

Hello, there.
This post is too old for now, but still found by goolge and misleading to newbies... So, I reply it.

The term 'SPL' indicates sound pressure level (i.e. How loud the sound is.) genereted by the same energy given.

In this case, those midranges; the 1220 and 1230 generate 93dB @ 1W.
That doesn't mean you get the same SPL when the same volume set.
Because almost all amplifiers today is voltage driven, the same volume set means the same voltage shall be given to the speaker(s). NOT the energy.
At the same voltage lower valued resister will consume more energy; Ohm's law.

For example, when the 1220 is driven at 1W, the voltage is calculated to 2.83V.
With 2.83V given, the 1230 is driven at 0.5W.
So you get the half SPL; 90dB. This will fit what you guess from the other manufacturer's example.

If you want to compare the Efficiency per energy, you have to use the way SPL @ 2.83V. And it is common to many manufacturer's specs.

PHL products are dedicated to SR or professional use, rather than home audio.
In the field of SR, Efficiency is more important. I guess that's why PHL represents SPL @ 1W instead of SPL @ 2.83V.

Regards,
Gustav1982
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Old 27th March 2010, 03:12 AM   #4
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The unit.
@1W means you differ the volume when you measure them.
If you want to know the SPL at the same volume, look at SPL@2.83V.
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Old 27th March 2010, 05:25 AM   #5
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Oops, I made a mistake... In the fifth sentence.

If you want to compare the SPL per voltage(the same volume potition), you have to use the way SPL @ 2.83V. And it is common to many manufacturer's specs.
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Old 27th March 2010, 09:44 AM   #6
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Quote:
Originally Posted by Gustav1982 View Post
For example, when the 1220 is driven at 1W, the voltage is calculated to 2.83V.
With 2.83V given, the 1230 is driven at 0.5W.
So you get the half SPL; 90dB.
Regards,
Gustav1982
You mean "so you get a loss of -3db"... this is naturally the relationship. But I observe especially by this PHL models by measuring only 0,3 (perhaps 0,4) db. This means, the efficiency is in fact the best in the 16 ohms version.

This PHL transducers for me the best midrange character 10 years ago for new individual loudspeaker projects. It was actually the successor from the old Audax PR170 series (same developer - as I know). PHL introduce arround 1996 additional bass suitable transducer in this size.
But a crossover design you should master (for me no problem because using of CAD support).
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Last edited by tiefbassuebertr; 27th March 2010 at 09:48 AM.
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Old 28th March 2010, 06:14 PM   #7
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Default Thanks for the assist.

Thanks for the assist, tiefbassuebertr.
I missed the difference.

I guess this is because of the stronger motor in the 1230.

The motor in the dynamic loudspeaker is mainly composed of the voice coil and the magnetic circuit.
Given the macnetic curcuit (magnet and pole-piece) is identical to both models, voice coil is the difference.

In many case, higher resistance model have longer wire in its voice coil; this means stronger magnetic field.

BL factor is the reference for the strength of magnetic curcuit.

By the way, I recommend the 2460(8") over the 1220.
They have better distortion profile and can be used more lower range.

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